Conveners
Algorithms and Machines
- Nigel Cundy
Algorithms and Machines
- Georg Bergner
Algorithms and Machines
- Hideo Matsufuru
Mr
Greg McGlynn
(Columbia University)
14/07/2015, 14:00
Algorithms and Machines
Talk
We discuss algorithmic improvements being used in the evolution of new 2+1+1 flavor lattices by the RBC/UKQCD collaboration. A technique similar to Hasenbusch mass splitting and suggested previously by Brower, Neff, and Orginos allows the light quark action to be split into multiple parts with different values of L_s, the size of the fifth dimension. This allows us to reduce chiral symmetry...
Chulwoo Jung
(Brookhaven National Laboratory)
14/07/2015, 14:20
Algorithms and Machines
Talk
Recent advances in hardware, combined with various deflation techniques has made it crucial to optimize not only for solver performances, but also for memory and disk footprint to keep the overall efficiency high.
Here we report on advances in Domain Wall Fermion formalism(DWF), such as zMobius which achieves a good approximation to the scaled Shamir DWF with smaller extent in 5th...
Mr
Andrea Bussone
(CP3-Origins, University of Southern Denmark)
14/07/2015, 14:40
Algorithms and Machines
Talk
Imposing twisted boundary conditions on the fermion fields is a procedure extensively used when evaluating, for example, form factors on the lattice. Twisting is usually performed for one flavour and only in the valence, and this causes a breaking of unitarity.
In this work we explore the possibility to restore the unitarity through the reweighting method. We evaluate the change in the...
Dr
Meifeng Lin
(Brookhaven National Laboratory)
14/07/2015, 15:00
Algorithms and Machines
Talk
The application of the Dirac operator on a spinor field, the Dslash operation, is the most computation-intensive part of the lattice QCD simulations. It is often the key kernel to optimize to achieve maximum performance on various platforms. Here we report on a project to optimize the domain wall fermion Dirac operator in Columbia Physics System (CPS) using the R-Stream source-to-source...
Prof.
Peter Boyle
(University of Edinburgh)
14/07/2015, 15:20
Algorithms and Machines
Talk
We discuss progress and performance from the development of a
data parallel interface for cartesian fields of tensor data types. The
library is suitable for the simulation of QCD including multiple grids.
Wherever appropriate the interface is quite similar to that of QDP++,
but the library makes use of C++11 features to reduce the volume of code,
compared to QDP++ while bringing...
Mr
Matthias Rottmann
(University of Wuppertal)
16/07/2015, 10:40
Algorithms and Machines
Talk
In this talk, we present a multigrid based eigensolver for computing low modes of the hermitian Wilson Dirac operator. For the non-hermitian case, multigrid methods have already replaced conventional Krylov subspace solvers in many lattice QCD computations. Since the gamma5 preserving aggregation based interpolation is valid for both, the hermitian and the non-hermitian case, inversions of...
Mr
Jakob Simeth
(University of Regensburg)
16/07/2015, 11:00
Algorithms and Machines
Talk
Disconnected contributions to hadronic quantities are noisy and still computationally challenging. Here, we explore the possibilities of Multigrid-based eigensolvers for Low-mode averaging and related methods.
Using only the few lowest approximate eigenmodes of the Hermitian Dirac operator $\gamma_5 M$ allows us to avoid expensive exact solves and improve the signal efficiently.
In this...
Dr
Hiroya Suno
(RIKEN Advanced Institute for Computational Science; RIKEN Nishina Center)
16/07/2015, 11:20
Algorithms and Machines
Talk
We are developing a computer code for calculating eigenvalues of the non-Hermitian O(a)-improved Wilson-Dirac operator. We introduce here the Sakurai-Sugiura method, which is an eigensolver algorithm based on a contour integral, allowing us to calculate desired eigenvalues located inside a given contour. We report the test results for low-lying eigenvalues obtained with free-case, quenched and...
Dr
Alexei Strelchenko
(FNAL)
16/07/2015, 11:40
Algorithms and Machines
Talk
We present a brief overview of deflation algorithms recently implemented in the SciDAC QUDA library
for solving the lattice-Dirac equation with multiple right-hand sides on NVIDIA accelerators.
In particular, we discuss implementation aspects of the mixed precision technique for the eigenvalue deflation which
helps to considerably relax GPU memory requirements while allowing for an...
Dr
M Clark
(NVIDIA)
17/07/2015, 16:30
Algorithms and Machines
Talk
We describe recent developments to the QUDA software framework, a library aimed at deploying lattice QCD computations on GPUs. The library has ever broadening support for various LQCD actions and algorithms, as well as being integrated into many LQCD applications. Recent focus has been on improving strong scaling for multi-GPU calculations and developing an adaptive multigrid solver. We...
Dr
hirokazu Kobayashi
(Intel K. K.)
17/07/2015, 16:50
Algorithms and Machines
Talk
We implemented lattice QCD on Xeon Phi coprocessor using intrinsics as vectorization method, and OpenMP and MPI as parallelization method. Our implementation uses double precision conjugate gradient (CG) solver which also supports multi-shift CG.
We present our optimization methodology and performance for key steps in CG algorithms.
Dr
Mario Schroeck
(INFN - Roma Tre)
17/07/2015, 17:10
Algorithms and Machines
Talk
We present the implementation of twisted mass fermions within the QPhiX code package along with an interface to tmLQCD. We analyze the performance on Intel Xeon Phis and Intel Xeon Haswell CPUs. On the latter we find a speedup of larger than 4x for the mixed precision conjugate gradient inverter.
Dr
Hidekatsu Nemura
(Center for Computational Sciences, University of Tsukuba)
17/07/2015, 17:30
Algorithms and Machines
Talk
We present our recent effort to develop the CUDA code to measure the Nambu-Bethe-Salpeter (NBS) wave function of various baryon-baryon systems on the lattice, which is a primary quantity to make a first-principle calculation of nuclear force and hyperonic-nuclear forces from lattice QCD. Not only the nucleon-nucleon (NN) but also the hyperon-nucleon (YN) and hyperon-hyperon (YY) interactions...
Mr
Jun Doi
(IBM Research - Tokyo)
17/07/2015, 17:50
Algorithms and Machines
Talk
As supercomputers are shifting from peta-scale to exa-scale, computers with accelerators such as GPUs, MICs and FPGAs have become one of the big trends of supercomputer because of their low energy consumption and high density. Now IBM’s POWER processor has quite new power, Nvidia’s Tesla GPU brings huge computational capability. It is important for us to understand how this new POWER+GPU...
